No response to my question, so I'll assume that this was the problem - when you specify the command you gave, the C:\Log folder must already exist. If it doesn't, it's not created for you because it might be an access issue (the folder exists but you don't
have write permissions to it). And because of the /quiet parameter, you wouldn't see the installation error message that says it can't access the folder, which would give you a big clue why the install was failing.
This was a great question, so thanks for posting it and I've updated that guide to make this clearer for the next person.
